3D printed brain model reveals physics of how human brains fold

Feb 1, 2016 | By Kira

An international team of researchers based in the US, Finland and France has used 3D printing technology to confirm an age-old question about how the human brain cortex ‘folds’ on itself to improve our cognitive function. The 3D printed brain model, based on MRI images of a ‘smooth’ fetal brain and 3D printed from various soft gels, mimicked how a real brain grows, revealing that the folded structure of human and certain other mammalian brains is determined by a physical growth process rather than a biological one, a finding that could have implications for diagnosing and even treating several neurological disorders, including Alzheimers, autism and schizophrenia.

As we all know from high-school biology class (or perhaps just from zombie movies), the human brain’s outer layer, known as the cortex, is covered with deep folds and wrinkles. What you might not have known, however, is that our brains actually start out completely smooth and only being to develop these folds at around the 20th week of gestation, with the process of folding—known as ‘gyrification’—continuing until we are about a year and half old.

Why our brains, along with some other animals including primates, elephants, dolphins and pigs, fold has been known for some time: essentially, it is a way to fit a larger cortex into a small volume (our skulls). A larger cortex surface means a larger number of cortical neurons, and therefore increased cognitive and intellectual capabilities.

The question of how our brains fold, however, has been puzzling neuroscientists for far too long. Some theories have suggested genetic, cellular, or other biological mechanisms as the cause of gyrification, however the ethical issues surrounding research on actual human brains have prevented more concrete proof.

Now, an international team of researchers from Harvard University, as well as Universities in Finland and France, have used 3D printing technology to create a realistic, tangible brain growth model, proving that, while there are several important molecular processes involved, the primary cause of brain folding is an “elementary mechanical instability” that essentially comes down to compression and buckling.

To prove this theory, the team created a multi-layered 3D printed gel model of a smooth fetal brain. Each layer was made from a different 3D printable soft gel, designed to expand at different degrees when immersed in a solvent. This uneven growth pattern was designed precisely to mimic how our actual brains develop at the fetal stage.

According to the researchers, within minutes of being submerged in the solvent, the outer layer of the 3D printed brain model began to swell relative to the underlying layers, and then mechanically compressed, leading to the formation of folds similar in size and shape to actual human brains. The researchers also created mathematical simulations based on the same initial geometry to further support their findings.

“We found that we could mimic cortical folding using a very simple physical principle and get results qualitatively similar to what we see in real fetal brains,” said Lakshminarayanan Mahadevan, a Professor of Applied Mathematics, Organismic and Evolutionary Biology and Physics, as well as a faculty member of the Wyss Institute for Biologically Inspired Engineering at Harvard.

"This simple evolutionary innovation, with iterations and variations, allows for a large cortex to be packed into a small volume, and is likely the dominant cause behind brain folding, known as gyrification," added Mahadevan.

Finally understanding the how of human brain folding could be key to understanding, diagnosing and potentially even treating brain-related disorders that are linked to malformation, brain size, cell migration and cortex thickness. Though the researchers point out that this 3D printed gel-based model still only predicts the behavior of simple, regular brain structures at the onset of the gyrification process, it is nevertheless in important step towards eventually recreating more complex and dynamic emerging folds.

The research was published in the academic journal Nature and Physics, and includes authors Tuomas Tallinen, Jun Young Chung, François Rousseau, Nadine Girard, Julien Lefèvre and L. Mahadevan. Participating research institutions include the Harvard John A. Paulson School of Engineering and Applied Sciences, the University of Jyvaskyla in Finland, the Institut Mines-Telecom and Aix-Marseille Université, both located in France.

I strongly believe that brain transplants are ethical because there are a variety of peple on this earth with a variety of different medical needs to be met. It's ethical..brain transplants. Please call me at 317 938 4171.

Folatt wrote at 2/4/2016 3:31:01 PM:

How ethical is this?Is this brain conscious?

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